Diamond film and method for producing the same

ABSTRACT

There is disclosed a method for producing a diamond film on a base material by a vapor phase reaction at least with introducing a raw material gas, wherein B(OCH 3 ) 3  gas is added to the raw material gas as a source of boron to be doped, and a diamond film is deposited on the base material by a vapor phase reaction utilizing the mixed raw material gas. There can be provided a method enabling easy and uniform production of a diamond film showing a low electric resistivity value with good reproducibility and few problems concerning handling such as serious bad influence on human bodies and explosiveness during the doping process.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a diamond film and a method forproducing the same.

[0003] 2. Related Art

[0004] In recent years, diamond films formed on base materials byutilizing unique properties of diamond have been widely investigated.For example, they are investigated as masking members for light exposurein lithography techniques used in the semiconductor device production,substrates for surface acoustic wave (SAW) devices, grinding andpolishing tools and so forth.

[0005] In recent years, use of diamond films as a masking membrane inthe X-ray lithography and electron beam lithography, which enablesformation of extremely fine patterns of 100 nm or less, utilizing theirproperties of high Young's modulus, etching resistance, high-energy rayirradiation resistance and so forth attracts attentions.

[0006] As the methods for producing a diamond film, there are knownmethods of depositing it on a base material by a vapor phase reactionusing DC arc discharge, DC glow discharge, combustion flame,radiofrequency wave (R.F.), microwave, hot filament and so forth. Amongthese production methods, the microwave CVD method and the hot filamentCVD method are generally used, since they enable formation of filmshaving a large size and good crystallinity.

[0007] Meanwhile, a raw material gas used in the aforementioned methodsof depositing on a base material by a vapor phase reaction is generallya mixed gas obtained by diluting a carbon-containing gas such asmethane, ethylene, acetylene and carbon monoxide with hydrogen gas.Electric resistivity of a diamond film obtained by performing a vaporphase reaction using such a hydrogen-diluted carbon-containing gas as araw material gas is in the range of 10⁹ to 10¹⁵ Ω.cm.

[0008] Further, when a diamond film showing an electric resistivityvalue in such a range is used, for example, as a mask for lithography,especially a mask for X-ray or electron beam lithography, a defect testof the mask must be performed by irradiation with an electron beam. Butthe resistivity is too high for the test, thus a charge up phenomenon islikely to occur due to accumulation of charged particles, and thereforesuch a defect test cannot be carried out quickly and precisely in manycases.

[0009] Moreover, when it is actually used as a mask for electron beamlithography, a high resistivity causes a problem in image transfer dueto the charge up.

[0010] Therefore, in order to avoid such a charge up phenomenon, it hasbeen proposed that a dopant gas such as diborane (B₂H₆) or phosphine(PH₃) is mixed with the aforementioned hydrogen-dilutedcarbon-containing gas during the production of a diamond film to performa vapor phase reaction and thereby reduce the electric resistivity valueof the diamond film.

[0011] Specifically, it is reported that, if B₂H₆ as a source of boronto be doped and hydrogen-diluted methane gas as a raw material gas aremixed, and then such a mixed raw material gas is introduced into achamber to perform a vapor phase reaction and thereby produce a diamondfilm of P-type, the electric resistivity value of the diamond film canbe decreased to 10⁻² Ω.cm (K. Marumoto, J. Appl. Phys., 31 (1992)4205-4209).

[0012] However, if B₂H₆ is used as the source of boron to be doped asdescribed above, influence on human bodies is feared, since thepermissible concentration thereof is 0.1 ppm. Further, when PH₃ is usedas the source of phosphorus to be doped, influence on human bodies issimilarly feared, since the permissible concentration thereof is 0.3ppm. That is, leakages even in a small amount are not accepted in dopingusing these gases. Furthermore, since they not only influence on humanbodies but also show explosiveness, and hence they have also a problemconcerning handling. Therefore, in order to use these gases, specialapparatuses for safety must be used for the apparatuses themselves,piping and so forth, and thus increase of cost is unavoidable.

[0013] With the purpose of obviating these problems, there has also beenproposed a method of adding boron by vaporizing a solution dissolvingB₂O₃ in methanol, ethanol, acetone or the like and mixing it with ahydrogen diluted raw material gas for use as a mixed raw material gas.However, this technique has a problem that it is difficult to produce auniform solution or control temperature of the solution, and thus it isdifficult to obtain a uniform diamond film with good reproducibility.

SUMMARY OF THE INVENTION

[0014] The present invention was accomplished in view of such problems,and its major object is to provide a method enabling easy and uniformproduction of a diamond film showing a low electric resistivity valuewith good reproducibility and few problems concerning handling such asserious bad influence on human bodies and explosiveness during thedoping process, at a low cost.

[0015] The present invention was accomplished in order to achieve theaforementioned object and provides a method for producing a diamond filmon a base material by a vapor phase reaction at least with introducing araw material gas, wherein B(OCH₃)₃ gas is added to the raw material gasas a source of boron to be doped, and a diamond film is deposited on thebase material by a vapor phase reaction utilizing the mixed raw materialgas.

[0016] If B(OCH₃)₃ gas is used as a source of boron to be doped in amethod of producing a diamond film on a base material by a vapor phasereaction with introducing raw material as described above, boron can beeasily and uniformly doped, and the electric resistivity value of theobtained diamond film can be reduced. That is, B(OCH₃)₃ gas shows littledanger concerning handling such as bad influence on human bodies andexplosiveness. Moreover, it enables easy and uniform doping of boron ina diamond film with good reproducibility. Therefore, when this diamondfilm is used, for example, as a mask for lithography, the charge upphenomenon in the defect test utilizing an electron beam can be avoided,and special apparatuses are not required, either. Therefore, the filmcan be produced at a low cost.

[0017] In the above method, the B(OCH₃)₃ gas is preferably added to theraw material gas to be introduced at a volume concentration of more than0 vol. % but 8 vol. % or less with respect to the total mixed rawmaterial gas.

[0018] If the volume concentration of the B(OCH₃)₃ gas with respect tothe total mixed raw material gas is more than 0 vol. % but 8 vol. % orless, a desired electric resistivity value can be obtained whilemaintaining high crystallinity.

[0019] In the above method, the doping of boron is preferably controlledso that the electric resistivity of the diamond film should become 10⁷Ω.cm or less at 20° C.

[0020] If the doping of boron is controlled so that the electricresistivity of the diamond film should become 10⁷ Ω.cm or less at 20° C.as described above, when this diamond film is used for a mask forlithography, especially a mask for X-ray or electron beam lithography,the charge up phenomenon can be surely avoided in a defect test of themask utilizing an electron beam. Thus, such a defect test can be quicklyand precisely performed. Therefore, it becomes easy to produce a diamondmask of high quality for lithography by utilizing the diamond film.

[0021] Moreover, since the charge up phenomenon can be avoided also whenthe mask is actually used as a mask for the electron beam lithography,it enables highly precise and highly efficient image transfer.

[0022] In the above method, when the diamond film is produced on thebase material, only a part of the film can be formed with addingB(OCH₃)₃ gas to the raw material gas, and the other part of the film canbe formed without adding B(OCH₃)₃ gas to the raw material gas. Moreover,in this case, the part of the film formed with adding B(OCH₃)₃ gas tothe raw material gas preferably has a thickness of 0.5 μm or less.

[0023] If only a part of the film is formed with adding B(OCH₃)₃ gas tothe raw material gas, and the other part of the film is formed withoutadding B(OCH₃)₃ gas to the raw material gas as described above, theamount of B(OCH₃)₃ used can be reduced. Therefore, desiredcharacteristics can be obtained while minimizing the degradation of thecrystallinity, and the cost can also be reduced.

[0024] Furthermore, the present invention provides a diamond filmuniformly doped with boron produced by the aforementioned productionmethod. This diamond film has a low electric resistivity, and thus itcan be used as a mask substrate that is unlikely to cause the charge upphenomenon during the defect test or use thereof.

[0025] The present invention further provides an apparatus for producinga diamond film on a base material by a vapor phase reaction withintroducing a raw material gas, which comprises, at least, a tank forsupplying raw material gas, an apparatus for supplying B(OCH₃)₃ gas as asource of boron to be doped, a chamber for depositing the diamond filmon the base material by a vapor phase reaction and an energy source forthe vapor phase reaction.

[0026] If an apparatus for producing a diamond film is constituted asdescribed above, a mixed raw material gas obtained by adding B(OCH₃)₃gas as a source of boron to be doped to a raw material gas can beintroduced to a chamber through an inlet pipe, and a diamond film dopedwith boron can be easily produced by a vapor phase reaction in thechamber at a low cost without providing conventionally used specialapparatuses for safety.

[0027] As explained above, according to the present invention, problemsconcerning danger of handling such as serious bad influence on humanbodies and explosiveness during the doping process are reduced by usingB(OCH₃)₃ instead of B₂H₆ or PH₃ which is generally used in conventionaltechniques, and thus special apparatuses as a safety measure becomeunnecessary. Moreover, the doping can be more easily and more uniformlyattained with good reproducibility compared with a case using avaporized solution of B₂O₂ dissolved in methanol, ethanol, acetone orthe like, which is used from the safety conscious viewpoint, as a sourceof boron to be doped.

[0028] As explained above, if B(OCH₃)₃ is used, and the doping amount ofboron is controlled so that the electric resistivity of the diamond filmshould become 10⁷ Ω.cm or less, the charge up phenomenon can be surelyavoided in a defect test of a mask required when the diamond film isused for a mask for lithography, especially a mask for X-ray or electronbeam lithography. Therefore, it becomes possible to produce a diamondmask of high quality for lithography. Moreover, since the charge upphenomenon can be avoided also when the mask is actually used as a maskfor the electron beam lithography, it enables highly precise and highlyefficient image transfer.

BRIEF EXPLANATION OF THE DRAWING

[0029]FIG. 1 is a schematic view showing a microwave CVD apparatus,which is an example of the apparatus according to the present invention.

PREFERRED EMBODIMENTS OF THE INVENTION

[0030] Hereafter, embodiments of the present invention will beexplained. However, the present invention is not limited to these.

[0031] The inventors of the present invention conceived that, in orderto easily and uniformly produce a diamond film having a low electricresistivity with few problems concerning handling such as serious badinfluence on human bodies and explosiveness and with goodreproducibility, B(OCH₃)₃ could be used as a source of boron to be dopedduring formation of a vapor phase synthesized diamond film, and thusaccomplished the present invention.

[0032]FIG. 1 is a schematic view showing a microwave CVD apparatus,which is a typical apparatus for producing a diamond film, provided withan apparatus for vaporizing and supplying B(OCH₃)₃ as an exemplarymicrowave CVD apparatus for the present invention.

[0033] In this microwave CVD apparatus 1, a base material stage 5provided with heating means such as a heater is disposed in a chamber 4provided with a gas inlet pipe 2 and a gas outlet pipe 3. Further, amicrowave power source 6 is connected to a microwave introduction window8 through a waveguide 7 so that plasma can be generated in the chamber4. Furthermore, an apparatus for supplying a mixed raw material gas isconnected at the other end of the gas inlet pipe 2, and a hydrogen gassupplying tank 14, a carbon-containing gas supplying tank 15 and, inparticular, an apparatus 9 for supplying B(OCH₃)₃ used for the presentinvention are provided on that side. In this supplying apparatus 9,there are provided a liquid B(OCH₃)₃ tank 10, a heater 11 for vaporizingB(OCH₃)₃, which is liquid at room temperature, and a mass flowcontroller 12 for precisely controlling the flow rate of B(OCH₃)₃.

[0034] Hereafter, the method for producing a diamond film by usingB(OCH₃)₃ as a source of boron to be doped in the production of a diamondfilm on a base material by a vapor phase reaction with introducing a rawmaterial gas will be explained with reference to FIG. 1.

[0035] First, when a diamond film is formed on a base material,generation density of diamond nuclei can be increased by providingdiamond particles on a base material surface, and thereby formation of avapor phase synthesized diamond film becomes easy. Therefore, to obtaina uniform continuous film even when it is a thin film, it is effectiveto perform a pretreatment for seeding diamond particles on the basematerial surface by coating of the base material surface with diamondsuspension, ultrasonication with diamond suspension, scratch treatmentwith diamond particles or the like.

[0036] A diamond film can be produced on a base material subjected tosuch a pretreatment by the vapor phase synthesis method utilizing, forexample, DC arc discharge, DC glow discharge, combustion flame,radiofrequency wave (R.F.), microwave, hot filament or the like as anenergy source. Among these production methods, the microwave CVD methodand the hot filament CVD method are preferred, since they enableformation of films having a large size and good crystallinity.

[0037] In the apparatus shown in FIG. 1, the microwave CVD method isused as an example of these vapor phase synthesis methods. A basematerial 13 subjected to a pretreatment as described above is placed onthe base material stage 5, and then inside of the chamber 4 is evacuatedby a non-illustrated rotary pump to a pressure of 10⁻³ Torr or less.

[0038] Then, a main constitutive raw material gas, for example, acarbon-containing gas such as methane, ethylene, acetylene and carbonmonoxide is supplied from the carbon-containing gas supplying tank 15 ata desired flow rate, and a mixed raw material gas consisting of the rawmaterial gas diluted with hydrogen gas supplied from the hydrogen gassupplying tank 14 and added with B(OCH₃)₃ gas according to the presentinvention at a predetermined concentration is introduced from the inletpipe 2 into the chamber 4.

[0039] At this time, the volume concentration of the B(OCH₃)₃ gas withrespect to the total mixed raw material gas is preferably controlled tobe more than 0 vol. % but 8 vol. % or less. If the vapor phase reactionis performed by using a mixed raw material gas added with B(OCH₃)₃ gasat a concentration more than 0 vol. %, the diamond film to be obtainedcan be doped with boron, and thus the electric resistivity thereof canbe reduced. Moreover, by controlling the concentration of the B(OCH₃)₃gas to be 8 vol. % or less, a desired electric resistivity value can beobtained while maintaining high crystallinity. If the B(OCH₃)₃ gasconcentration exceeds 8 vol. %, the boron concentration exceeds that ofthe saturated state, and doping of boron at a concentration exceedingthat level is difficult. Even though it is possible, the crystallinityis markedly degraded or generation of defects is increased, and thus itis not practically useful.

[0040] Then, after the opening degree of a valve of the gas outlet pipe3 is adjusted to obtain a pressure of 20 Torr in the chamber 4,microwaves are applied from the microwave power source 6 via thewaveguide 7 to generate plasma in the chamber 4 and thereby form adiamond film on the base material 13.

[0041] At this time, in order to control the film stress in the diamondfilm, the base material 13 may be heated by, for example, a heater suchas a sintered SiC heater included in the base material stage 5.

[0042] Boron may be doped only into a partial layer of the formeddiamond. For example, B(OCH₃)₃ may be added to dope boron only when alayer having a thickness of 0.5 μm or less is formed on a surface of theside irradiated with an electron beam (the side of base materialinterface) during use of the diamond film as an electron beam mask, andthe other part of the film may be formed without the doping. By doingso, the amount of B(OCH₃)₃ used can be reduced, thereby the degradationof crystallinity is minimized and the cost can also be reduced.

[0043] It is the most characteristic feature of the present inventionthat boron doping of diamond is attained by using a mixed raw materialgas containing B(OCH₃)₃ in the vapor phase synthesis.

[0044] By replacing the source of boron to be doped from conventionallyand generally used B₂H₆ or PH₃ to B(OCH₃)₃ as described above, problemsconcerning danger of handling such as serious bad influence on humanbodies and explosiveness are ameliorated, and thus special apparatusesfor safety become unnecessary. Moreover, it becomes possible to moreeasily and more uniformly dope boron into a diamond film with betterreproducibility compared with a case where a solution dissolving B₂O₃,which has been used from the safety conscious viewpoint, in methanol,ethanol, acetone or the like is vaporized and used as the source ofboron to be doped.

[0045] By controlling the B(OCH₃)₃ gas concentration added to the rawmaterial gas, the electric resistivity value of the diamond film to beproduced can be controlled. In particular, if it is controlled so thatthe electric resistivity of the diamond film should become 10⁷ Ω.cm orless, the charge up phenomenon can surely be avoided in a defect test ofa mask which is required when the diamond film is used as a mask forlithography, especially a mask for X-ray or electron beam lithography.Thus, it becomes possible to produce diamond for lithography of highquality. Moreover, when the film is actually used as a diamond mask forelectron beam lithography, the charge up phenomenon can also be avoided,and thus it becomes possible to perform highly precise and highlyefficient image transfer.

EXAMPLES

[0046] Hereafter, the present invention will be specifically explainedwith reference to an example and a comparative example.

Example 1

[0047] A single crystal silicon wafer having a diameter of 100 mm,thickness of 2 mm and crystal orientation of <100>, of which bothsurfaces were polished, was prepared as a base material and subjected toa pretreatment in order to improve the generation density of diamondnuclei. First, the base material was adsorbed on a spin coater by vacuumsuction, and 50 ml of suspension of diamond particles (cluster diamondshaving a mean particle size of 50 nm) was dropped onto the surface. Thewafer was rotated at 3000 rpm for 30 seconds to obtain uniformly coatedstate of the suspension of diamond particles on the surface. Then, thecoated suspension was air-dried to form a seeded layer of diamond on thebase material surface. After the pretreatment was performed as describedabove, the base material was set on the base material stage in thechamber of the microwave CVD apparatus shown in FIG. 1.

[0048] Then, after reduced pressure of 10⁻³ Torr or less was obtained byevacuation using a rotary pump, a mixed raw material gas consisting ofmethane, hydrogen gas and B(OCH₃)₃ gas was supplied from the gas inletpipe. The gases were introduced into the chamber at 40.0 sccm formethane gas, 940.0 sccm for hydrogen gas and 20.0 sccm for B(OCH₃)₃ gasto obtain a volume ratio of methane gas/hydrogengas/B(OCH₃)₃=4.0/94.0/2.0. Then, opening degree of the valve of the gasoutlet pipe was controlled to obtain a pressure of 20 Torr in thechamber, and plasma was generated by applying microwaves of 3000 W toform a boron-doped diamond film on the base material for 2 hours.

[0049] During the film formation, the base material generated heat dueto absorption of the microwaves, and the surface temperature reached860° C.

[0050] A boron-doped diamond film obtained as described above wasfinished by polishing. In a 35 mm square region at the center of thebase material, the thickness was 0.50 μm±0.04 μm, stress was 60 MPa±12MPa, and surface roughness was 3 nm in terms of Ra, and thus they wereat highly practically useful levels. In addition, little fluctuation wasobserved among batches, which was practically very advantageous.

[0051] Furthermore, the above diamond film formed substrate wasprocessed into a mask substrate for electron beam lithography, and astencil type mask for electron beam lithography was produced by usingthe mask substrate. Then, the value of electric resistivity of thediamond film was measured, and it was found to be 0.6 Ω.cm. Thus, evenwhen a defect test of the mask was performed, the charge up phenomenonwas not caused. Moreover, also when it was actually used as a mask forelectron beam lithography, there was no charge up phenomenon, and stableand highly precise image transfer was possible.

Comparative Example 1

[0052] A diamond film was formed in the same manner as in the example 1except that the B(OCH₃)₃ gas was not used as a source of boron to bedoped, and instead a solution dissolving B₂O₃ in ethanol was vaporizedto add to the raw material gas. That is, on the surface of the siliconwafer subjected to the pretreatment where the diamond suspension wasspin-coated, a boron-doped diamond film was formed on the base materialfor 3.5 hours by introducing a mixed raw material gas having acomposition for obtaining a diamond film showing crystallinity(confirmed by the Raman spectrometry) and electric resistivity(confirmed by the four-terminal method) of the same levels as thoseobtained in the example 1 (methane gas/hydrogen gas/B₂O₃gas=1.0/97.0/2.0) into the chamber and applying microwaves of 3000 W at20 Torr to generate plasma, and then the wafer was polished. Althoughthe obtained diamond showed reduced resistivity of 30 Ω.cm, thicknessand stress showed bad uniformity, i.e., the thickness was 0.50 μm±0.11μm and the stress was 150 MPa±60 MPa in a 35 mm square region at thecenter of the base material.

[0053] Moreover, fluctuation of the concentration of the B₂O₃ solutionin ethanol was observed as the B₂O₃ solution was consumed, andtemperature control was strictly required during the process. Thus, itwas extremely difficult to obtain a uniformly doped diamond in terms ofuniformity in a film and among batches. Furthermore, a large amount ofgenerated B₂O₃ particles adhered, and thus it was disadvantageous alsoin view of prevention of defect generation.

[0054] (B₂H₆ Doping)

[0055] First of all, when a diamond film having characteristics of thesame levels is formed by using B₂H₆ as a source of boron to be dopedwithout using B(OCH₃)₃ gas, a safety measure for apparatuses to beprepared must be completely different from those of the example 1. Thatis, the permissible concentration of B₂H₆ for human bodies is 0.1 ppm,and it shows extremely high explosiveness, i.e., the explosion limitthereof is 0.9 to 98.0 vol. %. Therefore, enormous cost is required forinstallations for preventing leakage of B₂H₆. Moreover, in order toobtain a conductivity of the same level as that of the example 1, B₂H₆must be added at a concentration of several vol. %, and it is anextremely dangerous concentration.

[0056] After all, since use of B₂H₆ was too unpractical taking economy,safety and characteristics of diamond to be obtained into consideration,a comparison test was given up.

[0057] The present invention is not limited to the embodiments describedabove. The above-described embodiments are mere examples, and thosehaving the substantially same configuration as that described in theappended claims and providing the similar functions and advantages areincluded in the scope of the present invention.

[0058] For example, while the use of the diamond film of the presentinvention was explained for cases where it is used as a masking memberfor X-ray or electron beam lithography, the present invention is notlimited to this use.

What is claimed is:
 1. A method for producing a diamond film on a basematerial by a vapor phase reaction at least with introducing a rawmaterial gas, wherein B(OCH₃)₃ gas is added to the raw material gas as asource of boron to be doped, and a diamond film is deposited on the basematerial by a vapor phase reaction utilizing the mixed raw material gas.2. The method for producing a diamond film according to claim 1, whereinthe B(OCH₃)₃ gas is added to the raw material gas to be introduced at avolume concentration of more than 0 vol. % but 8 vol. % or less withrespect to the total mixed raw material gas.
 3. The method for producinga diamond film according to claim 1, wherein the doping of boron iscontrolled so that electric resistivity of the diamond film shouldbecome 10⁷ Ω.cm or less at 20° C.
 4. The method for producing a diamondfilm according to claim 2, wherein the doping of boron is controlled sothat electric resistivity of the diamond film should become 10⁷ Ω.cm orless at 20° C.
 5. The method for producing a diamond film according toclaim 1, wherein, when the diamond film is produced on the basematerial, only a part of the film is formed with adding B(OCH₃)₃ gas tothe raw material gas, and the other part of the film is formed withoutadding B(OCH₃)₃ gas to the raw material gas.
 6. The method for producinga diamond film according to claim 2, wherein, when the diamond film isproduced on the base material, only a part of the film is formed withadding B(OCH₃)₃ gas to the raw material gas, and the other part of thefilm is formed without adding B(OCH₃)₃ gas to the raw material gas. 7.The method for producing a diamond film according to claim 3, wherein,when the diamond film is produced on the base material, only a part ofthe film is formed with adding B(OCH₃)₃ gas to the raw material gas, andthe other part of the film is formed without adding B(OCH₃)₃ gas to theraw material gas.
 8. The method for producing a diamond film accordingto claim 4, wherein, when the diamond film is produced on the basematerial, only a part of the film is formed with adding B(OCH₃)₃ gas tothe raw material gas, and the other part of the film is formed withoutadding B(OCH₃)₃ gas to the raw material gas.
 9. The method for producinga diamond film according to claim 5, wherein the part of the film formedwith adding B(OCH₃)₃ gas to the raw material gas has a thickness of 0.5μm or less.
 10. The method for producing a diamond film according toclaim 6, wherein the part of the film formed with adding B(OCH₃)₃ gas tothe raw material gas has a thickness of 0.5 μm or less.
 11. The methodfor producing a diamond film according to claim 7, wherein the part ofthe film formed with adding B(OCH₃)₃ gas to the raw material gas has athickness of 0.5 μm or less.
 12. The method for producing a diamond filmaccording to claim 8, wherein the part of the film formed with addingB(OCH₃)₃ gas to the raw material gas has a thickness of 0.5 μm or less.13. A diamond film produced by the method according to claim
 1. 14. Adiamond film produced by the method according to claim
 2. 15. A diamondfilm produced by the method according to claim
 3. 16. A diamond filmproduced by the method according to claim
 5. 17. A mask substrateutilizing the diamond film according to claim
 13. 18. A mask substrateutilizing the diamond film according to claim
 14. 19. A mask substrateutilizing the diamond film according to claim
 15. 20. An apparatus forproducing a diamond film on a base material by a vapor phase reactionwith introducing a raw material gas, which comprises, at least, a tankfor supplying a raw material gas, an apparatus for supplying B(OCH₃)₃gas as a source of boron to be doped, a chamber for depositing thediamond film on the base material by a vapor phase reaction and anenergy source for the vapor phase reaction.